Mina-Lou Schleith | Searcharxiv

arXiv2026

Superconductivity from emergent dipolar interactions in a fractionalized Fermi liquid

Starting from the spin-fermion model or Hertz-Millis theory describing electrons coupled to anti-ferromagnetic spin fluctuations we develop a theory to describe the transition from a fractionalized Fermi liquid into a $d_{x^2-y^2}$ superconductor. We focus on small electron doping on top of the half-filled state. The doped electrons enter the system as spinon-chargon bound states, which form a small, reconstructed Fermi surface. The bound states are neutral under the emergent U(1) gauge symmetry of the fractionalized Fermi liquid, but interact via a dipolar two-body potential. We show that because of the projective action of translation symmetry on the spinons and chargons, the Fourier components of this repulsive dipolar interaction are peaked at the anti-ferromagnetic wave vector, thereby providing a robust microscopic mechanism for $d_{x^2-y^2}$ pairing in a fractionalized metal.

cond-mat.supr-con↗

arXiv2025

Anyon dispersion from non-uniform magnetic field on the sphere

The discovery of fractional quantum anomalous Hall states in moiré systems has raised the interesting possibility of realizing phases of itenerant anyons. Anyon dispersion is only possible in the absence of continuous magnetic translation symmetry (CMTS). Motivated by this, we consider anyons on the sphere in the presence of a non-uniform magnetic field which breaks the ${\rm SU}(2)$ rotation symmetry, the analog of CMTS on the sphere, down to a ${\rm U}(1)$. This allows us to study the energy dispersion of the anyons as a function of $L_z$ angular-momentum, while maintaining the perfect flatness of single-particle dispersion. We parametrize the non-uniform field by a real parameter $R$ which concentrates the field at the north (south) pole for $R>1$ ($R < 1$), and show that, for our choice of field, any $p$-body correlation function evaluated in the space of Laughlin quasiholes can be mapped \emph{exactly} to a corresponding $p$-body correlation function in uniform field. In the thermodynamic limit, this enables us to analytically compute the interaction-generated spatially varying potential felt by the anyons. Remarkably, such spatially varying potential is sufficient to generate dispersion for the anyons, which we compute exactly, up to an overall scaling constant. The anyon dispersion in our model describes azimuthal motion around the sphere at a constant height, similar to spin precession. Our work therefore serves as a concrete demonstration that interaction alone can generate nonzero anyon dispersion in the presence of inhomogeneous magnetic field.

cond-mat.str-el↗